Happy 30th! How the blue chip index has moved with the times

In 1935 two journalists had an idea. They wanted to create an amalgam of the leading shares quoted on the London Stock Exchange that would indicate how the market, and therefore by extension British industry, was performing.

So the FT 30, or FT Ordinary Index, was born. It was not just a question of totting up the share prices of the 30 biggest companies and deriving an average out of that. First, Maurice Green and Otto Clarke wanted the more actively traded companies — no “dead wood”, as Mr Clarke, the mathematical brains of the team, said.

Second, some companies were bigger than others and their performance had to be weighted to reflect this, so the index truly reflected the market’s movement.